Banana connector

Invented in 1924 by Richard Hirschmann, the banana connector' (commonly banana plug for the male and banana socket for the female), is a single-wire electrical connector used for joining wires to equipment. The term 4mm connector is also used, although not all banana connectors will mate with 4 mm parts. While signal wires must be shielded, control voltage connections need no shielding. Banana plugs can be stacked.